title: High body mass index is associated with increased diurnal strains in the articular cartilage of the knee.
abstract: OBJECTIVE
  Obesity is an important risk factor for osteoarthritis (OA) and is associated with changes in both the biomechanical and inflammatory environments within the joint. However, the relationship between obesity and cartilage deformation is not fully understood. The goal of this study was to determine the effects of body mass index (BMI) on the magnitude of diurnal cartilage strain in the knee.
  
  
  METHODS
  Three-dimensional maps of knee cartilage thickness were developed from 3T magnetic resonance images of the knees of asymptomatic age- and sex-matched subjects with normal BMI (18.5-24.9 kg/m2) or high BMI (25-31 kg/m2). Site-specific magnitudes of diurnal cartilage strain were determined using aligned images recorded at 8:00 AM and 4:00 PM on the same day.
  
  
  RESULTS
  Subjects with high BMI had significantly thicker cartilage on both the patella and femoral groove, as compared to subjects with normal BMI. Diurnal cartilage strains were dependent on location in the knee joint, as well as BMI. Subjects with high BMI, compared to those with normal BMI, exhibited significantly higher compressive strains in the tibial cartilage. Cartilage thickness on both femoral condyles decreased significantly from the AM to the PM time point; however, there was no significant effect of BMI on diurnal cartilage strain in the femur.
  
  
  CONCLUSIONS
  Increased BMI is associated with increased diurnal strains in articular cartilage of both the medial and lateral compartments of the knee. The increased cartilage strains observed in individuals with high BMI may, in part, explain the elevated risk of OA associated with obesity or may reflect alterations in the cartilage mechanical properties in subjects with high BMI.
authors.affiliation: Duke University and Duke University Medical Center, Durham, North Carolina.
authors.forename: Margaret R
authors.initials: MR
authors.lastname: Widmyer
authors.forename: Gangadhar M
authors.initials: GM
authors.lastname: Utturkar
authors.forename: Holly A
authors.initials: HA
authors.lastname: Leddy
authors.forename: Jeremy L
authors.initials: JL
authors.lastname: Coleman
authors.forename: Charles E
authors.initials: CE
authors.lastname: Spritzer
authors.forename: Claude T
authors.initials: CT
authors.lastname: Moorman
authors.forename: Louis E
authors.initials: LE
authors.lastname: DeFrate
authors.forename: Farshid
authors.initials: F
authors.lastname: Guilak
mesh_terms: D015992:Body Mass Index; D002358:Cartilage, Articular / Q000473:pathology / Q000503:physiopathology*; D016022:Case-Control Studies; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000473:pathology / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D009765:Obesity / Q000150:complications / Q000503:physiopathology*; D020370:Osteoarthritis, Knee / Q000453:epidemiology / Q000503:physiopathology; D012307:Risk Factors; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology*